The present invention relates generally to a throttle control system for an automotive vehicle, which has an accelerator mechanically independent of a throttle valve, and which controls the throttle valve angular position depending upon the accelerator operating position. More specifically, the invention relates to a throttle control system which eliminates influences of noise components within an accelerator position indicative signal which otherwise adversely affects drivability and riding comfort.
Such throttle valve position control systems have been disclosed in European Patent First Publications 01 14 401, 01 21 937, 01 21 938, and 01 21 939. In these prior proposals or developments, the throttle valve angular position is generally controlled by an electromagnetic actuator associated with the throttle valve. A throttle control signal is produced depending upon the degree of depression of an accelerator pedal as indicated by a signal generated at the accelerator pedal.
A similar throttle control system has also been disclosed in the Japanese Patent First Publication (Tokkai) Showa 56-107925, published on Aug. 27, 1981. This document discloses an electronic fuel injection control system for a spark ignition internal combustion engine, which includes a throttle valve servo mechanism operative to control a throttle valve angular position depending upon the degree of depression of an accelerator pedal.
The aforementioned control systems are capable of controlling the throttle valve to a desired angular position corresponding to the depression rate of the accelerator pedals. Therefore, those systems may be successful in controlling air induction at a rate corresponding to the accelerator depression degree. Theoretically, control of the throttle valve angular position implies direct control of engine output to obtain desired engine performance. However, in practice, due to production errors among individual engines and the wide range of possible environmental conditions, engine output does not necessarily correspond to the demand on the engine throughout the range of throttle valve angular positions.
There have been proposals for controlling engines or power trains including the engine and a power transmission to obtain output torque precisely corresponding to the output demand. SAE Technical Paper 830423, by the Society of Automotive Engineering, discloses a power train control system controlling the engine in a discrete manner by controlling the power transmission. In controlling the engine, the engine controller detects data from various points in the engine and adjusts fuel supply, ignition timing, EGR flow rate and intake air flow rate to optimal values derived from computations on the detected data. In controlling the transmission, a transmission controller detects engine load and vehicle speed, and derives the gear ratio to be established by the transmission and performs lock-up control on the basis of the results of computations on the detected data.
In such electrical throttle control system, since the accelerator operating magnitude is converted into a signal value corresponding thereto, vibration of the accelerator due to vibration of the vehicle body or repeated depressing and releasing of the accelerator will affect throttle control. For instance, the accelerator pedal may vibrate when the vehicle body vibration is at a significant level. This accelerator vibration causes variation of the accelerator position signal values and thereby changes of throttle valve angular position. By change of the throttle valve angular position, the engine output through the power train changes correspondingly. Frequent change of engine output results in degrading drivability and riding comfort of the vehicle.
Especially, when the engine vibration or vibration transmitted through the vehicular suspension is in a frequency range near or within a natural frequency of the vehicle body, the vehicle body vibration may become significant to affect throttle control. In this case, the relatively highly frequency component due to accelerator vibration may be included in the accelerator position indicative signal as a noise component thereof.